Abstract
In this paper we present a number of classes of solutions of the Einstein's field equations with variable G, Lambda and bulk viscosity for a Kaluza-Klein type of cosmological model. The solutions are obtained by using gamma-law equation of state p = (gamma - 1)rho, where adiabatic parameter gamma-varies continuously as the universe expand. A unified description of the early evolution of the universe is discussed with number of possible assumption on the bulk viscous term and gravitational constant in which an inflationary phase followed by radiation-dominated phase. We also investigate the cosmological model with constant and time dependent bulk viscosity along with constant and time dependent gravitational constant. In all cases, the cosmological constant Lambda found to be positive and decreasing function of time which supports the results obtained from recent supernovae Ia observations. The important physical behaviour of the early cosmological model has also been discussed in the frame work of higher dimensional space-time.